1. Knowledge Of Things That Are Relevant To Us Is Attainable If We Pursue That Knowledge In Ways Consistent With The Nature of The Universe Therefore it is an error to think that knowledge must be based on "forms" or "models" or "ideals" that are held to exist in another reality. This error leads to the belief that the things we experience around us originate from and are to be understood according to those nonexistent "forms." (Plato and others) It is an error to think that knowledge must be based on "essences" that are held to exist as a part within the things we experience around us, This error leads to the belief that the things we experience around us originate and are to be understood according to these nonexistent "essences." (Aristotle and others) It is an error to think that knowledge must be based on divine revelation or by reference to "gods" or "prime movers" who create all things according to their divine will. This error leads to the belief that the things around us originated and are to be understood according to religion. (Judaism, Christianity, and others)
2. Knowledge should be pursued by studying the facts of nature, which means that we must remember that we ourselves, as well as the subject of our knowledge, and our means of considering that knowledge, derive from (1) the eternal properties of the elementary matter, and (2) the temporary qualities of the bodies that are formed by the combinations of elementary matter and void.
3. The Faculties of Observation Provided By Nature Are The Tools By Which We Measure Truth. These are three in number and are collectively referred to as the Epicurean "Canon of Truth." They are (1) the "five senses," (2) the "feeings" of pleasure and pain, and (3) the "anticipations.
4. We should not seek to understand everything equally well, nor should we expect to understand that which is not possible for us to understand. We should seek to have firm convictions about those things which are necessary for our peace of mind. From the Letter to Pythocles: "In the first place, remember that, like everything else, knowledge of celestial phenomena, whether taken along with other things or in isolation, has no other end in view than peace of mind and firm convictions. We do not seek to wrest by force what is impossible, nor to understand all matters equally well, nor make our treatment always as clear as when we discuss human life or explain the principles of physics in general—for instance, that the whole of being consists of bodies and intangible nature, or that the ultimate elements of things are indivisible, or any other proposition which admits only one explanation of the phenomena to be possible."
5. "Reason" and "logic" are not in themselves faculties of observation like the three categories of the Canon of Truth. Diogenes Laertius - Biography of Epicurus: Every sensation, he says, is devoid of reason and incapable of memory; for neither is it self-caused nor, regarded as having an external cause, can it add anything thereto or take anything therefrom. Nor is there anything which can refute sensations or convict them of error: one sensation cannot convict another and kindred sensation, for they are equally valid; nor can one sensation refute another which is not kindred but heterogeneous, for the objects which the two senses judge are not the same; nor again can reason refute them, for reason is wholly dependent on sensation; nor can one sense refute another, since we pay equal heed to all. And the reality of separate perceptions guarantees the truth of our senses. But seeing and hearing are just as real as feeling pain. Hence it is from plain facts that we must start when we draw inferences about the unknown. For all our notions are derived from perceptions, either by actual contact or by analogy, or resemblance, or composition, with some slight aid from reasoning.
6. Therefore the opinions derived from "reason" or "logic" must constantly be tested against the data obtained from the canonical faculties. Opinions formed by reason should be concluded to be "true" when clear available evidence supports the conclusion, and no clear evidence contradicts the conclusion. Opinions formed by reason should be concluded to be "false" when clear available evidence contradicts the conclusion, and no clear evidence supports the conclusion. Opinions formed by reason which are not based on data from our faculties of observation, or on which the data from our faculties of observations is unclear, must not be considered "true," but considered "speculative" at best, and we must "wait" for additional evidence before concluding that the assertion is either true or false.
References and additional detail for this list may be found here.
Discussion of this FAQ entry is here.
Epicurus was considered a "dogmatist" because he held that confidence in certain conclusions is possible. Epicurus did not consider it necessary to have omniscience in order to be confident is stating that something can be known. He was very careful, however, to point out the limitations of the senses and the need to verify conclusions and to be open to new facts. Please see the discussion of epistemology in the FAQ here.